Upconversion luminescence nanoparticles(UCNPs)have shown promising applications in biomedical fields as luminescent probes because of their excellent advantages such as single excitation with multicolor emission,low autofluorescence,and deep penetration.But the biological applications of such nanomaterials are still restricted due to the unfavorable surface properties.In this work,we develop a facile one-pot hydrothermal route to obtain O-carboxymethyl chitosan(OCMC)-wrapped NaYF4:Yb3+/Tm3+/Er3+red UCNPs which have been used for targeted cell luminescence imaging directly and efficiently.The successful coating of the UCNPs by OCMC has been confirmed by Fourier-transform infrared(FTIR)spectroscopy and dynamic light scattering(DLS)studies.Transmission electron microscopy(TEM),powder X-ray diffraction(XRD),thermogravimetric analysis(TGA),and photoluminescence(PL)spectra have been used to characterize the size,composition and emission color of the samples,respectively.Due to the good biocompatibility,water-solubility,and strong UC luminescence,these hydrophilic nanocrystals will open up new avenues in further bioapplications.
Graphene oxide(GO) is an important derivative of graphene, fascinating the entire world with its dazzling properties and versatile performance. However, the synthesis of GO via chemical routes often results in limited control of the density of functionalities and their distribution, presenting a barrier to the spread of GO applications. We modified Hummers' method and aimed at controlling the oxygen functionality of GO. The highest oxygen content of the modified synthetic GO(Md GO) occurs at edge regions, and the large proportion of carboxyl groups can be easily removed upon annealing. The excellent conductivity of intrinsic graphene can thus be recovered after the removal of the main functional groups. The resulting Md GO was reduced and doped with NH3, and the reduced Md GO(r Md GO) was determined to be an excellent support for oxygen reduction reaction(ORR) electrocatalysts. As a demonstration, a composite of Co O and N-r Md GO was fabricated, which exhibited highly comparable ORR performance in alkaline relative to 20 wt.% Pt/C.
This paper describes a robust method for the synthesis of high-quality ZIF-8 nanocrystals using reverse micelles as discrete nanoscale reactors.The precise size control of ZIF-8 nanocrystals is conveniently achieved by tuning the concentration of precursors,reaction temperatures,the amount of water,and the structure of surfactants.The as-synthesized ZIF-8 nanocrystals are of narrow distribution and tunable size.A size-dependent catalytic activity for Knoevenagel condensation reaction is further demonstrated by using ZIF-8 nanocrystals with different sizes as the catalysts.This facile method opens up a new opportunity in the synthesis of various ZIFs nanocrystals.
A facile one-pot synthetic strategy is developed to prepare high-quality Pt supercubes. The as-synthesized Pt supercubes are composed of the uniform Pt nanocubes arranged in a primitive cubic structure. The shape and size of the Pt superparticles are readily tuned by varying the structures of pyridyl-containing ligands used in the synthesis. The co-presence of CO and nitrogen-containing ligands is critical to the formation of Pt supercubes. While CO molecules play an important role in the synthesis of Pt nanocube, introducing nitrogen-containing ligands is essential to the successful assembly of those nanocubes into Pt supercubes. Our systematic studies reveal that the electrostatic attraction between positively charged ligands and nega- tively charged Pt nanocubes is the main driving force for the assembly of Pt nanocubes into supercubes. More importantly, the ligands within the Pt supercubes are readily removed at relatively low expected to exhibit unique size-selective catalysis. temperature to yield surface-clean supercubes which are
